Remove from the heat and stir in the flavorings (everything but the melon); let cool completely. Strain into a small bowl or measuring cup.

In a blender, working in two batches, puree half the simple syrup mixture and half the melon until smooth. Strain into a metal loaf pan or square pan; repeat with remaining syrup and melon. Cover and freeze until set, about 8 hours.

When ready to serve, using a fork, scrape the surface of the melon ice to create large flakes. Transfer to glasses, top with a splash of soda water, and serve with additional fruit, if desired.